Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel.
As a result, kinds of applications using the secondary battery are being increased owing to advantages of the secondary battery, and hereafter the secondary battery is expected to be applied to more applications and products than now.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle- or large-sized devices, such as vehicles, use a middle- or large-sized battery module having a plurality of battery cells electrically connected with one another because high power and large capacity are necessary for the middle- or large-sized devices.
The size and weight of the battery module is directly related to the receiving space and power of the corresponding middle- or large-sized device. For this reason, manufacturers are trying to manufacture small-sized, light-weight battery modules. Furthermore, devices, which are subject to a large number of external impacts and vibrations, such as electric bicycles and electric vehicles, require stable electrical connection and physical coupling between components constituting the battery module. In addition, a plurality of battery cells are used to accomplish high power and large capacity, and therefore, the safety of the battery module is regarded as important.
Preferably, the middle- or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle- or large-sized battery module. Especially, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the weight of the pouch-shaped battery is small, and the manufacturing costs of the pouch-shaped battery are low.
In order to connect pouch-shaped batteries in series and/or in parallel to one another, electrode terminals of the respective batteries are electrically connected to one another via an electrode terminal connecting member. In this case, however, separation between the electrode terminals of the respective batteries and the electrode terminal connecting member may occur, or the electrode terminal connecting member may be dislocated, due to external force, such as vibration and external impact or twist caused by expansion of the batteries, with the result that a short circuit of the battery module may occur.
In order to prevent the occurrence of the short circuit, therefore, there has been proposed a structure in which the electrode terminal connecting member is mounted to the battery cells via a predetermined insulating member. In this case, however, an additional member is needed, and, in addition, the member must be mounted to the battery cells, with the result that the overall size of the battery module is increased, and the structure of the battery module is complicated. Furthermore, such a structure secures only stable mounting of the electrode terminal connecting member to the battery cells but does not provide a structural stability of the battery module.